Am 19.08.2011 17:53, schrieb Sergio Campamá:
> Thanks for the insight into the problem. The thing is that I have a
> task scheduler, a linked list that, well, lists the tasks to
> perform... Since linked lists are dynamic in nature, I need malloc to
> create the new "task" and append it to the list.. And after the task
> is done, I free the task and
> go on to the next one... The other place I use linked lists is to
> maintain a list of timers that the application uses to signal certain
> events... after
> the timer activates, it also gets freed...
>
> So that is why I need malloc and can't (or don't know how) to do it
> with other types of dynamic storage, or static. (On that subject,
> what other types of dynamic storage exist?)
just because you use a linked list does not automatically mean that you
also need dynamic memory.
i also implemented an event handler that uses a linked list. an event_t
is a struct with the information about the event. each module that wants
to use an event allocates its own object as [static] global. each event
can only be enqueued once.
pro:
- each module is responsible for its own memory
- all statically allocable
- exactly as many event objects as are needed
con:
- entire struct in RAM, including the function pointer which will not
change.
an other possibility is to have an array of objects [structs] and your
own allocate (and free) function that returns pointers to that array.
that way you also get statically allocated memory.
pro:
- all statically allocable
- also possible to use indexes instead of pointers. indexes are easier
to check if they are valid (compared to pointers). and a single byte
is usually enough.
con:
- you also have to make two design descisions:
- how many objects will be needed (array size). do you go for a
typical size or worst case size?
- what will you do if no object can be allocated?
(if selected size < worst case size)
- it does not automatically adjust to the application (e.g. if you have
different variants. the solution above only uses the RAM when the
modules are linked)
chris
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